Method of making copper cathode starting sheets



United States Patent Ofiice 3,046,203 Patented July 2d, 1962 METHOD OF MAKING COPPER CATHODE STARTENG SHEETS Graham M. Cadweil, Black Eagle, Mont, assignor to The Anaconda Company, a corporation of Montana No Drawing. Filed Nov. 20, 1959, Ser. No. 854,258 5 Claims. Cl. 204-42) This invention relates to the preparation of copper cathode starting sheets used in the electrolytic refining of copper and, more particularly, to the preparation of such starting sheets by the electrolytic deposition of pure copper on the surface of a smooth copper plate and the removal of the deposited copper therefrom substantially in the form of the starting sheet. The method of the invention is characterized in that a substantially continuous film of an aqueous emulsion is disposed over the surface of the plate prior to the electrodeposition of copper thereon to prevent adherence between the deposited copper and the plate.

Copper cathode starting sheets are ordinarily prepared by electrolytically depositing a thin layer of copper over the surface of a smooth rolled copper'plate and then stripping the deposited copper from the plate in sheet form. A groove is usually defined in the plate along its side and bottom edges so that when the deposited copper is stripped from the plate it comes off substantially in the form of a rectangular sheet with straight edges. It is also common practice to coat the surface of the plate with a film ofhydrocarbon oil before it is placed in the cell so that the deposited copper separates cleanly from the plate without adhering thereto or tearing during removal. The oils commonly employed as separating agents in this manner are light insoluble petroleum oils of the type generally used for lubrication.

This .conventional method of making copper cathode starting sheets is not entirely satisfactory, however, because the oils used as separating agents do not always spread continuously over the surface of the plate. It sometimes happensthatthefilm of oil is broken in places, with the result that deposited copper adheres to the surface of the plate at the discontinuities in the film and prevents the sheet from being separated intact from the plate. Also, some portions of the oil films are often formed substantially thicker than others and consequently are not covered by a deposit of copper during the electrolytic process. Hence, holes and other breaks appear in the finished sheet and it must be discarded as scrap. Considerable care must be exercised, therefore, in applying known separating agents to the plates to insure that no discontinuities or substantial variations in thickness are present in the film.

It is the purpose of the present invention to provide a method for making starting sheets in which a new separating agent is used rather than the insoluble hydrocarbon oils of the type now employed which do not form satisfactory films. to achieve by use of this new separating agent a marked reduction in the number of starting sheets which adhere to the plates or are formed with holes or gaps. Hence, the separating agent must be capable of being disposed in a continuous and uniformly thick film over the surface of the plates.

A further object of the invention is the provision of a method which does not require excessive care in the disposition of the film of separating agent over the plate, so that the time required to preparea plate for the electrolytic cells is considerably reduced. It is also an object of the invention to provide a method of making starting sheets wherein the separating agent employed is not flammable and is consequently less dangerous than the insoluble hydrocarbon oils previously used.

It is also an object of the invention,

The method of the invention by which these objects are achieved comprises disposing a substantially continuous film of a water-soluble oil emulison over the surface of a smooth copper plate. Pure copper is then elecover this film and the electrolytically deposited copper is stripped from the copper plate substantially in the form of the starting sheet. The substantially continuous film of the water-soluble oil emulsion prevents adherence between the deposited copper and the copper plate.

Water-soluble oil emulsions of the type contemplated for use in this new method are prepared by mixing a major amount of Water with a minor amount of one of the soluble oil lubricants or coolants commercially available, Which usually consists essentially of a mineral oil, an emulsifying agent, and. a coupling agent. A typical soluble-oil lubricant might contain from to percent by weight of a light petroleum oil and from 10 to 20 percent by weight of a combination of emulsifying agents and coupling agents. Emulsifying agents commonly used include one or more nonionic, anionic, or cationic emulsifiers, aryl-alkyl polyester sulfonates and alcohols, hexitol anhydride fatty acid esters, sorbitan monopalmitate, monolaurate, monostearate, and monoleate, polyoxyethylene derivatives of these sorbitan compounds, and alkylnaphthalene sulfonates. Satisfactory coupling agents (i.e., agents soluble both in oil and in Water) include alcohols, glycols and glycol ethers. In addition to these three basic components (viz. the mineral oil, emulsifying agent, and coupling agent), the soluble-oil lubricant may also contain small amounts of water, antifoaming agents, and germicides.

In general, the emulsion is prepared by agitating one part by weight of the soluble oil lubricant in 10 to 50 parts by weight of water. This produces an emulsion which is sufiiciently low in viscosity to be disposed easily and quickly over the surface of the starting sheet blank to produce a continuous film without requiring excessive care for its application. At the same time, the emulsion is viscous enough so that thefilm can retain its continuity and uniform thickness on the plate even when the plate is suspended vertically in the electrolytic cell.

It has been found that despite the water-dispersable characteristics of the oil coating on the starting sheet blank, it does not wash away when the blank is immersed in the aqueous copper electrolyte. It has also been found that it is much easier to distribute the soluble oil emulsion uniformly over the surface of such blank than is a conventional light oil, and that the film of oil emulsion on the blank retains its continuity exceptionally Well. As a result, starting sheets deposited over a soluble oil film are notably freer from holes or tears than starting sheets deposited over the usual insoluble oil film, and yet are very easy to strip from the blank.

In one example of the method of the invention, an emulsion was prepared by emulsifying 7.65 parts by weight of a petroleum oil having a viscosity of Saybo1tseconds at 100 F. in 90 parts by weight of water. To this were added 0.9 part by weight of mahogany soap and 0.18 part by weight of sodium oleate as emulsifying agents, and 0.19 part by weight of a die'thylene glycol ether as a coupling agent. Also, 0.01 part by weight of a dimethylpolysiloxane anti-foaming agent and 0.01 part by Weight of a germicide were added to the emulsion.

The emulsion was spread continuously over the entire surface of a smooth rolled copper plate which had grooves formed adjacent its bottom and side edges. The plate was suspended in an electrolytic cell containing a commercial electrolyte composed primarily of a copper sulfate solution. An anode of standard composition was also placed in the cell and copper from the anode was electrolytically deposited on the plate for a period of 24 aoaaaoa hours until a firm deposit of copper about inch thick had formed over the plate. The plate was then taken from the cell and the electrolytically deposited copper was stripped therefrom between the grooves substantially in the form of the starting sheet without adhering to the plate or evidencing any holes or gaps.

I claim:

1. The method of making pure copper cathode starting sheet for use in the electrolytic refining of copper which comprises disposing! a substantially continuous film of a water-base oil emulsion over the surface of a smooth copper plate, electrolytically depositing pure copper on the surface of said copper plate over said film, and stripping the electrolytically deposited copper from said copper plate substantially in the form of a starting sheet, whereby the substantially uniformly thick continuous film of the water-base soluble oil emulsion prevents adherence between said deposited copper and said copper plate.

2. The method of making pure copper cathode starting sheets for use in the electrolytic refining of copper which comprises disposing over the surface of a smooth copper plate a substantially continuous film of an emulsion comprising a major amount of water and a minor amount of a mineral oil lubricant emulsified therein, electrolytically depositing pure copper on the surface of said plate over said film, and stripping the electrolytically deposited copper trom said copper plate substantially in the form of said starting sheet, whereby the substantially uniformly thick continuous film of the waterbase soluble oil emulsion prevents adherence between said deposited copper and said copper plate.

3. The method of making pure copper cathode starting sheets for use in the electrolytic refining of copper which comprises disposing over the surface of a smooth copper plate a substantially continuous film of an aqueous emulsion comprising water, a mineral oil, and an emulsifying agent, electrolytically depositing pure copper on the surface of said copper plate over said film; and stripping the electrolytically deposited copper from said copper plate substantially in the form of a starting sheet, whereby the substantially uniformly thick continuous film of said water-base soluble oil emulsion prevents adherence between said deposited copper and said copper plate.

4. The method of making pure copper cathode starting sheets for use in the electrolytic refining of copper which comprises disposing over the surface of a smooth copper plate a substantially continuous film of an emulsion comprising a major amount of water and a minor amount of a soluble-oil lubricant emulsified therein, said soluble oil lubricant consisting essentially of from about to percent by weight of a petroleum base oil and from about 10 to about 20 percent by weight of an emulsifying agent and a coupling agent; electrolytically depositing pure copper on the surface of said copper plate over said film; and stripping the electrolytically deposited copper from said copper plate substantially in the form of the starting sheet, whereby the substantially uniformly thick continuous film of said water-base soluble oil emulsion prevents adherence between said deposited copper and said copper plate.

5. The method of making pure copper cathode starting sheets for use in the electrolytic refining of copper which comprises disposing over the surface of a smooth copper plate a continuous film or a water-base soluble oil emulsion comprising from about 80 to about 90 percent by weight of water and from about 10 to about 20 percent by weight of a soluble-oil lubricant emulsified therein, said soluble oil lubricant constsiting essentially of from about 80 to about 90 percent by weight of a petroleumbase oil and from about 10 to about 20 percent by weight of an emulsifying agent and a coupling agent, electrolytically depositing pure copper on the surface of said copper plate over said film, and stripping the electrolytically deposited copper from said copper plate substantially in the form of the starting sheet, whereby the substantially uniformly thick continuous film of said water-base soluble oil emulsion prevents adherence between said deposited copper and said copper plate.

Reterences ited in the file of this patent Bennett: Practical Emulsions, Chemical Publication Co., New York, 1943, pages 92 and 93. 

2. THE METHOD OF MAKING PURE COPPER CATHODE STARING SHEETS FOR USE IN THE ELECTROYTIC REFINING OF COPPER WHICH COMPRISES DISPOSING OVER THE SURFACE OF A SMOOTH COPPER PLATE A SUBSTANTIALLY CONTINUOUS FILM OF AN EMULSION COMPRISING A MAJOR AMOUNT OF WATER AND A MINOR AMOUNT OF A MINERAL OIL LUBRICANT EMULSIFIED THEREIN, ELECTROLYTICALLY DISPOSITING PURE COPPER ON THE SURFACE OF SAID PLATE OVER SAID FILM, AND STRIPPING THE ELECTROLYTICALLY DEPOSITED COPPER FROM SAID COPPER PLATE SUBSTANTIALLY IN THE FORM OF SAID STARTING SHEET, WHEREBY THE SUBSTANTIALLY UNIFORMLY THICK CONTINUOUS FILM OF THE WATER-BASE SOLUBLE OIL EMULSION PREVENTS ADHERENCE BETWEEN SAID DEPOSITED COPPER AND SAID COPPER PLATE. 